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Ralph Keeling - UC San Diego. La Jolla, CA, US

Ralph Keeling Ralph Keeling

Professor | UC San Diego


Ralph Keeling's research focuses on atmospheric composition, the carbon cycle, and climate change.




Ralph Keeling Publication




The Keeling Curve animation




Keeling is a professor of geochemistry in the Geosciences Research Division of Scripps Institution of Oceanography at the UC San Diego.

His research focuses on atmospheric composition, the carbon cycle, and climate change. He is considered a leading investigator of the global oxygen cycle known for precise measurements and analysis techniques.

Keeling is also considered a leading global authority on carbon dioixde and the global greenhouse effect associated with emissions of the gas through human activities. He serves as director of the Scripps CO2 Program, which maintains observations of atmospheric carbon dioxide records at the Mauna Loa Observatory in Hawaii, as well as other sampling stations throughout the world. The Mauna Loa record, also known as the Keeling Curve, was initiated in 1956. Daily updates of the atmospheric CO2 concentration can be found at keelingcurve.ucsd.edu.

Keeling developed his method for measuring atmospheric oxygen levels utilizing interferometry techniques in the laboratory. He began pioneering measurements of changes in atmospheric oxygen levels from air samples collected at stations around the world. The measurements continue at nine sampling stations, extending from Ellesmere Island in northern Canada over the equator to two Antarctic stations.

Measurements from his group show that the atmosphere O2 is decreasing at a small but measurable rate due primarily to the burning of fossil fuels. From 1991 to 2011, the atmosphere lost on average 19 out of every million O2 molecules in the atmosphere. Establishing this rate was a milestone for improving our understanding of the processes controlling the buildup of CO2 in the atmosphere.

Born in La Jolla, Calif., Keeling received a B.S. in physics, summa cum laude, from Yale University, and a Ph.D. in applied physics from Harvard University.

He previously served as a visiting scientist at the National Center for Atmospheric Research (NCAR). He completed postdoctoral fellowships at NCAR and Harvard.

He received the Rosenstiel Award from the University of Miami’s Rosenstiel School of Marine and Atmospheric Science, the Outstanding Publication Award from NCAR, and was an H. Burr Steinbach Scholar at Woods Hole Oceanographic Institution. He also was a Climate Center Visitor at Columbia University’s Lamont-Doherty Earth Observatory.

Keeling is a member of the American Geophysical Union.

Areas of Expertise (5)

Atmospheric Gasses

Air-sea Gas Exchange

Atmospheric Oxygen

Paleoclimate and Climate Change

Global Carbon Cycle

Accomplishments (3)

Humboldt Research Award

2009 In recognition of his career achievement

H. Burr Steinbach Visiting Scholar at Woods Hole Oceanographic Institution

1998 Woods Hole Oceanographic Instituition

Rosenstiel Award


Education (2)

Harvard University: Ph.D., Applied Physics

Yale University: B.S, Physics

Affiliations (2)

  • Atmospheric Oxygen Research Group at SIO
  • Scripps CO2 Program

Media Appearances (2)

Greenhouse gas reaches alarming new record

CNN  online


Passing 410 ppm "is important because it punctuates another milestone in the upwards march of CO2," according to Ralph Keeling, head of the Scripps CO2 program at Scripps Institution of Oceanography in California.

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Earth's carbon dioxide levels continue to soar, at highest point in 800,000 years

USA Today  online


“We keep burning fossil fuels. Carbon dioxide keeps building up in the air,” said Scripps scientist Ralph Keeling, who maintains the longest continuous record of atmospheric carbon dioxide on Earth. “It’s essentially as simple as that.” Ralph Keeling and his late father Charles David Keeling have kept carbon dioxide (CO2) measurements at the Mauna Loa Observatory in Hawaii since 1958.

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Articles (4)

Wave inhibition by sea ice enables trans-Atlantic ice rafting of debris during Heinrich events

Earth and Planetary Science Letters

Wagner, TJW, Dell RW, Eisenman I, Keeling RF, Padman L, Severinghaus JP.

2018 The last glacial period was punctuated by episodes of massive iceberg calving from the Laurentide Ice Sheet, called Heinrich events, which are identified by layers of ice-rafted debris (IRD) in ocean sediment cores from the North Atlantic. The thickness of these IRD layers declines more gradually with distance from the iceberg sources than would be expected based on present-day iceberg drift and decay. Here we model icebergs as passive Lagrangian particles driven by ocean currents, winds, and sea surface temperatures. The icebergs are released in a comprehensive climate model simulation of the last glacial maximum (LGM), as well as a simulation of the modern climate. The two simulated climates result in qualitatively similar distributions of iceberg meltwater and hence debris, with the colder temperatures of the LGM having only a relatively small effect on meltwater spread. In both scenarios, meltwater flux falls off rapidly with zonal distance from the source, in contrast with the more uniform spread of IRD in sediment cores. To address this discrepancy, we propose a physical mechanism that could have prolonged the lifetime of icebergs during Heinrich events. The mechanism involves a surface layer of cold and fresh meltwater formed from, and retained around, large densely packed armadas of icebergs. This leads to wintertime sea ice formation even in relatively low latitudes. The sea ice in turn shields the icebergs from wave erosion, which is the main source of iceberg ablation. We find that sea ice could plausibly have formed around the icebergs during four months each winter. Allowing for four months of sea ice in the model results in a simulated IRD distribution which approximately agrees with the distribution of IRD in sediment cores.

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Revision of global carbon fluxes based on a reassessment of oceanic and riverine carbon transport

Nature Geoscience

Resplandy, L, Keeling RF, Rodenbeck C, Stephens BB, Khatiwala S, Rodgers KB, Long MC, Bopp L, Tans PP.

2018 Measurements of atmospheric CO2 concentration provide a tight constraint on the sum of the land and ocean sinks. This constraint has been combined with estimates of ocean carbon flux and riverine transport of carbon from land to oceans to isolate the land sink. Uncertainties in the ocean and river fluxes therefore translate into uncertainties in the land sink. Here, we introduce a heat-based constraint on the latitudinal distribution of ocean and river carbon fluxes, and reassess the partition between ocean, river and land in the tropics, and in the southern and northern extra-tropics. We show that the ocean overturning circulation and biological pump tightly link the ocean transports of heat and carbon between hemispheres. Using this coupling between heat and carbon, we derive ocean and river carbon fluxes compatible with observational constraints on heat transport. This heat-based constraint requires a 20-100% stronger ocean and river carbon transport from the Northern Hemisphere to the Southern Hemisphere than existing estimates, and supports an upward revision of the global riverine carbon flux from 0.45 to 0.78 PgC yr(-1). These systematic biases in existing ocean/river carbon fluxes redistribute up to 40% of the carbon sink between northern, tropical and southern land ecosystems. As a consequence, the magnitude of both the southern land source and the northern land sink may have to be substantially reduced.

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Assessing fossil fuel CO2 emissions in California using atmospheric observations and models

Environmental Research Letters

Graven, H, Fischer ML, Lueker T, Jeong S, Guilderson TP, Keeling RF, Bambha R, Brophy K, Callahan W, Cui X, Frankenberg C, Gurney KR, LaFranchi BW, Lehman SJ, Michelsen H, Miller JB, Newman S, Paplawsky W, Parazoo NC, Sloop C, Walker SJ.

2018 Analysis systems incorporating atmospheric observations could provide a powerful tool for validating fossil fuel CO2 (ffCO(2)) emissions reported for individual regions, provided that fossil fuel sources can be separated from other CO2 sources or sinks and atmospheric transport can be accurately accounted for. We quantified ffCO(2) by measuring radiocarbon (C-14) in CO2, an accurate fossil-carbon tracer, at nine observation sites in California for three months in 2014-15. There is strong agreement between the measurements and ffCO(2) simulated using a high-resolution atmospheric model and a spatiotemporally-resolved fossil fuel flux estimate. Inverse estimates of total in-state ffCO(2) emissions are consistent with the California Air Resources Board's reported ffCO(2) emissions, providing tentative validation of California's reported ffCO(2) emissions in 2014-15. Continuing this prototype analysis system could provide critical independent evaluation of reported ffCO(2) emissions and emissions reductions in California, and the system could be expanded to other, more data-poor regions.

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How does the terrestrial carbon exchange respond to inter-annual climatic variations? A quantification based on atmospheric CO2 data


Rodenbeck, C, Zaehle S, Keeling R, Heimann M.

2018 The response of the terrestrial net ecosystem exchange (NEE) of CO2 to climate variations and trends may crucially determine the future climate trajectory. Here we directly quantify this response on inter-annual timescales by building a linear regression of inter-annual NEE anomalies against observed air temperature anomalies into an atmospheric inverse calculation based on long-term atmospheric CO2 observations. This allows us to estimate the sensitivity of NEE to inter-annual variations in temperature (seen as a climate proxy) resolved in space and with season. As this sensitivity comprises both direct temperature effects and the effects of other climate variables co-varying with temperature, we interpret it as "inter-annual climate sensitivity". We find distinct seasonal patterns of this sensitivity in the northern extratropics that are consistent with the expected seasonal responses of photosynthesis, respiration, and fire. Within uncertainties, these sensitivity patterns are consistent with independent inferences from eddy covariance data. On large spatial scales, northern extratropical and tropical interannual NEE variations inferred from the NEE-T regression are very similar to the estimates of an atmospheric inversion with explicit inter-annual degrees of freedom. The results of this study offer a way to benchmark ecosystem process models in more detail than existing effective global climate sensitivities. The results can also be used to gap-fill or extrapolate observational records or to separate inter-annual variations from longer-term trends.

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